Throughout the business world, inkjet printing systems are extensively used for image reproduction. Inkjet printing systems frequently make use of one or more inkjet printheads mounted within a carriage that is moved back and forth across print media, such as paper. For example, the carriage may include a single printhead that is capable of printing a single color (i.e., black), a single printhead capable of printing multiple colors (i.e., black, cyan, magenta and yellow), a first printhead capable of printing one color (i.e., black) and a second printhead capable of printing multiple colors (i.e., cyan, magenta and yellow), or four printheads each capable of printing a single color. As the carriage is moved across the print media, a control system activates the printhead(s) to deposit or eject ink droplets onto the print media to form images and text. Such systems may be used in a wide variety of applications, including computer printers, plotters, copiers and facsimile machines.
Ink is provided to the printhead(s) mounted to the carriage by one or more supplies of ink that are either carried by the carriage or mounted to the printing system such that the supplies of ink do not move with the carriage. For the case where the ink supplies are not carried with the carriage, the ink supplies can be in fluid communication with the printhead(s) to replenish the printhead(s) or the printhead(s) can be intermittently connected with the ink supplies by positioning the printhead(s) proximate to a filling station to which the ink supplies are connected whereupon the printhead(s) are replenished with ink from the refilling station.
For the case where the ink supplies are carried with the carriage, one ink supply may be integral with each printhead whereupon the entire printhead and ink supply is replaced when ink is exhausted. Alternatively, the ink supplies can be carried with the carriage and can be separately replaceable from the printhead(s).
For convenience, the concepts of the invention are discussed in the context of thermal inkjet printheads. A thermal inkjet printhead die includes an array of firing chambers having orifices (also called nozzles) which face the print media. The ink is applied to individually addressable ink energizing elements (such as firing resistors) within the firing chambers. Energy provided by the firing resistors heats the ink within the firing chambers causing the ink to bubble. This in turn causes the ink to be expelled out of the orifice of the firing chamber toward the print media. As the ink is expelled, the bubble collapses and more ink is drawn into the firing chambers, allowing for repetition of the ink expulsion process.
Typically to increase print media throughput (i.e. to increase the speed of printing per page of print media), it is to necessary to increase the firing rate of the firing chambers, maximize the density of the firing chambers (i.e. firing resistors) and/or increase the number of firing chambers. With regards to increasing the firing rate of the firing chambers, the ability to do this somewhat limited by ink composition and the heat generated by the process of repeatedly firing the firing chambers. Hence, the ability to increase the print media throughput of a printing system by increasing the firing rate of the firing chambers of the printhead(s) is somewhat limited given the already high firing frequency of printhead firing chambers.
Maximizing the density of the firing chambers and/or increasing the number of firing chambers to increase print media throughput, typically necessitates an increase in the size of the printhead die and/or a miniaturization of printhead die components. With regards to miniaturization of the printhead die components, once a certain degree of miniaturization has been reached, conventional manufacturing by assembling separately produced components becomes more difficult and costly. In addition, the substrate that supports firing resistors, the barrier that isolates individual resistors, and the orifice plate that provides a nozzle above each resistor are all subject to small dimensional variations that can accumulate to limit miniaturization. Further, the assembly of such components for conventional printheads requires precision that limits manufacturing efficiency. Hence, increasing the print media throughput of a printing system by miniaturization of printhead die components of the printhead(s) is somewhat limited by manufacturing practicalities and costs.
With regards to increasing the size of the printhead die to increase print media throughput, printheads employing Page Wide Arrays (PWA's) have already been developed. In a PWA printhead, the firing chambers extend across the full width of the print media thereby eliminating the need of the carriage supporting the PWA printhead to be moved back and forth across the print media. In other words, to perform a full page printing operation using a PWA printhead, the print media need only be stepped past the PWA printhead while the PWA printhead remains stationary. This elimination of the movement of the PWA printhead results in an increase in print media throughput. Although the use of a PWA printhead increases print media throughput, there are some disadvantages to the use of PWA printheads. Namely the cost associated with manufacturing PWA printhead die components and the subsequent cost to consumers of replacing a PWA printhead at the end of printhead life.
As such, there is a need for printing systems with increased print media throughput. In particular, there is a need for an increased print media throughput printing system that makes use of conventional, non PWA printheads that can be moved back and forth across the print media.